1. Field of the Invention
The present invention relates to a circuit for displaying characters on a video raster in the form of discrete character images.
2. Description of the Prior Art
Video data display units utilizing a cathode-ray tube to produce images on a raster screen in the form of discrete blocks are known in the art. Such devices utilize a portion of the screen for display which is divided into fields arranged in lines and columns. Character images are produced by directing an electron beam at discrete portions of the field designated by line and column positions. Only such designated areas are illuminated, resulting in an image on the screen corresponding to a designated character.
The information associated with each character controlling which portions of the raster are to be illuminated is stored in a character generator in the form of a point matrix. Each point of the point matrix in the character generator corresponds with a character point or block of the character to be displayed, said blocks or points occupying a discrete area of the raster. The information associated with each character is taken line by line from the character generator and displayed on the raster.
The graphic quality of the displayed character is dependent upon size of the discrete points and upon the number of individual points per character. Increased resolution and refinement in the shape of the character displayed can be achieved by decreasing the size of the discrete points, however, a correspondingly increased band width is required to transmit such a character line in order to accommodate the increased information bits.